Onboard to the OSS Community Develocity Instance

[cdsap]

Onboard to the OSS Community Develocity Instance

This PR adds Develocity Build Scan® and Build Cache support
for this project, publishing to the OSS Community Develocity Instance at
https://community.develocity.cloud under project ID ebay.

What this PR adds

• The Develocity Gradle plugin and the Common Custom User Data Gradle
  plugin, applied at the latest released versions.
• settings.gradle.kts pointing the build at https://community.develocity.cloud and
  associating builds with project ebay.
• A "Revved up by Develocity" badge in the README linking to the filtered Build Scan list
  for this project's root project name.
• A setup step in each GitHub Actions workflow that runs the build, so CI publishes Build
  Scans automatically using a short-lived access token.

Step 1 — Get an access key for community.develocity.cloud

Build Scan publishing and Build Cache writes from CI need a Develocity access key.

1. Visit https://community.develocity.cloud.
2. Sign in as the CI service account that the Develocity Solutions team has provisioned
   for your project — that account was shared with you out-of-band when this onboarding
   was set up. The access key inherits that account's project memberships and permissions,
   which is exactly what you want for CI.
3. From the user menu in the top-right, open My settings → Access keys.
4. Click Generate access key, give it a description (e.g. GitHub Actions), and copy
   the generated key. Keep this tab open until you complete Step 2 — the key is only
   shown once.

Step 2 — Set the GitHub Actions secret on this repository

CI uses a repository secret named DEVELOCITY_ACCESS_KEY to authenticate to
community.develocity.cloud.

1. Open this repository on GitHub.

2. Click Settings.

3. In the left sidebar, click Secrets and variables → Actions.

4. Click New repository secret. (If a DEVELOCITY_ACCESS_KEY secret already exists,
   click its Update button instead.)

5. Set Name to:

   DEVELOCITY_ACCESS_KEY
   

6. Set Secret to the value below, replacing PASTE_THE_ACCESS_KEY_FROM_STEP_1_HERE
   with the key you copied in Step 1:

   community.develocity.cloud=PASTE_THE_ACCESS_KEY_FROM_STEP_1_HERE
   

   The community.develocity.cloud= prefix is required — without the host name, the
   access key is silently ignored. This is the most common point of failure when
   onboarding, so please double-check the format.

7. Click Add secret (or Update secret).

Step 3 — Provision an access key for your local builds

Developers building this project locally should provision an access key for
community.develocity.cloud so their Build Scans publish and they get reads
from the remote Build Cache. The Develocity Gradle plugin's
provisionDevelocityAccessKey task does this in a single command — it opens
the browser, asks the developer to confirm, and writes the key to
~/.gradle/develocity/keys.properties automatically.

Before running this command, sign out of community.develocity.cloud in
your browser (or use a private/incognito window) so the access key gets
associated with your personal account, not the CI service account you
signed in as for Step 1.

./gradlew provisionDevelocityAccessKey

Note on the CI run on this PR

This PR was prepared from a fork. Forks can't read your repository's secrets, so the
workflow run on this PR cannot publish to community.develocity.cloud even after you set
the secret in Step 2.

If you want CI verification before merging, push the branch
dv/onboard-oss-community-develocity-instance to a temporary branch on this repo (not
the fork) and re-run the workflow there — it will pick up the secret and publish a Build
Scan.

After merging, every CI run on this repository will publish a Build Scan to
https://community.develocity.cloud. CI runs from forks of this repository will not (forks
don't have access to the secret either), and that's expected.

[mcumings]

This is awesome, thanks a ton!

[mcumings]

Looks like we need to add this to the workflows as well, in order for CI to be detected properly